A known drive system for a vehicle disclosed in each of JP2009-101730A, JP2006-137406A, and JP2010-6190A (hereinafter referred to as References 1, 2, and 3) includes a transmission to which a driving force of an engine is transmitted from an output shaft of the engine, and a clutch mechanism arranged between the output shaft of the engine and an input shaft of the transmission. According to the drive system disclosed in each of References 1, 2, and 3, the clutch mechanism includes a first clutch portion arranged at the output shaft of the engine, and a second clutch portion arranged at the input shaft of the transmission. The clutch mechanism is switchable between a connected state where the first and second clutch portions are engaged with each other to thereby transmit the driving force of the engine to the transmission and a disconnected state where the first and second clutch portions are disengaged from each other to thereby block the transmission of the driving force of the engine to the transmission.
According to the drive system disclosed in each of References 1, 2, and 3, when the clutch mechanism is brought into the connected state or into the disconnected state under a condition where the input shaft of the transmission is in rotation, a hydraulic pressure caused by a centrifugal force due to the rotation (hereinafter, the hydraulic pressure caused by the centrifugal force due to the rotation will be referred to as a centrifugal hydraulic pressure) may influence operational responsiveness of the clutch mechanism when the clutch mechanism shifts between the connected and disconnected states. As a result, improvement of the operational responsiveness of the clutch mechanism may be limited. In addition, the centrifugal hydraulic pressure due to the rotation is influenced by a rotating speed of the input shaft. Accordingly, the operational responsiveness of the clutch mechanism may be influenced by a moving speed of the vehicle, therefore limiting the improvement of the operational responsiveness of the clutch mechanism.
A need thus exists for a drive system for a vehicle, which is not susceptible to the drawback mentioned above.